Atomically Dispersed WN 3 O Sites on Defective Graphitic Carbon Nitride Enabling Efficient and Selective Photocatalytic Depolymerization of Lignin Models and Larch Lignin

ABSTRACT Lignin valorization still is challenging of efficient and selective production of highly‐functionalized aromatic compounds. Here atomically dispersed WN 3 O sites on defective g‐C 3 N 4 (W 1 /C V ‐OCN) are fabricated by an in situ route, in which WN 3 O sites are stabilized on C V ‐OCN through reinforcing W─N (O) coordination interactions. The W 1 /C V ‐OCN exhibit excellent photocatalytic oxidation activity and selectivity in the depolymerization of lignin models and larch lignin. Under the conditions of 25°C, O 2 atmosphere and simulated sunlight irradiation, the optimal 0.96%W 1 /C V ‐OCN catalyst shows nearly complete conversion of a wide range of β‐O‐4 and β‐1 lignin models, alongside more than 90% of C α ─C β bond cleavage selectivity; particularly, the depolymerization of larch lignin is achieved over 0.96%W 1 /C V ‐OCN, affording 8.4% of benzaldehyde and 24.7% of guaiacol as the main products after 4 h light irradiation. Reaction mechanism studies reveal that single WN 3 O sites not only facilitate lignin activation through photoinduced O‐to‐W charge transfer to produce alkoxy radical intermediates but also accelerate charge separation and transfer dynamics through directional electron transfer along W─N (O) bonds and dynamic transformation of W 6+ /W 5+ states to ensure the formation of plentiful reactive oxygen species (ROSs). Precise β‐scission (C α ─C β and/or C β ─O bonds breakage) is achieved by synergy of alkoxy radical intermediates and ROSs.